Optical position sensor

Abstract

An optical sensor for sensing the radial position of a shaft. Detection of radial movement is made when a larger or smaller portion of a light beam incident on the shaft is blocked. In order to obtain a light beam of small diameter a laser light source or fiber optic system may be used. To provide long term stability the shaft is provided with a flat or with groove that is machined around its periphery to pass the entire light beam to a detector. This signal provides AGC compensation for the light source, detector and optical system.

What is claimed: 
     
       1. An optical position sensor for sensing radial position of a shaft comprising: a light source;   means for directing a beam of light from said source toward said shaft so that a portion of said beam is blocked by said shaft and a second portion of said beam is allowed to pass by said shaft;   a light detector for detecting the portion of said beam allowed to pass by said shaft;   the portion of said beam allowed to pass by said shaft providing a measure of the position of said shaft;   means for periodically permitting during normal motion of said shaft all of said beam to pass by said shaft to said detector and thereby cause said detector to produce a maximum output signal;   means for periodically preventing during normal motion of said shaft any of said beam from reaching said detector and thereby cause said detector to produce a minimum output signal;   the maximum and minimum output signals from said detector being useful for compensating for changes in output of the light source, changes in sensitivity of the detector, and changes in transmission properties of the directing means.   
     
     
       2. The invention according to claim 1, wherein the means for periodically permitting all of said beam to pass by said shaft comprises a groove around said shaft. 
     
     
       3. The invention according to claim 2, wherein the means for preventing any of said beam from reaching said detector comprises an enlarged diameter area on said shaft. 
     
     
       4. The invention according to claim 1, wherein the means for periodically permitting all of said beam to pass by said shaft comprises a flat on said shaft. 
     
     
       5. A method for sensing radial position of a shaft comprising the steps of: providing a light source;   directing a beam of light from said source toward said shaft so that a first portion of said beam is blocked and a second portion of said beam is allowed to pass by said shaft;   detecting the portion of said beam allowed to pass by said shaft;   the portion of said beam allowed to pass by said shaft providing a measure of the position of said shaft;   periodically permitting during normal motion of said shaft all of said beam to pass by said shaft to said detector and thereby cause said detector to produce a maximum output signal;   periodically preventing during normal motion of said shaft any of said beam from reaching said detector and thereby cause said detector to produce a minimum output signal;   the maximum and minimum output signals from said detector being useful for compensating for changes in output of the light source and changes in sensitivity of the detector.